In a normal human eye, light enters through the cornea and passes through the pupil, and the natural crystalline lens focuses the light onto the retina of the eye. However, due to cataracts or other problems, the natural crystalline lens of an eye may need to be replaced with an artificial intraocular lens (IOL). The term “pseudophakia” is used to describe an eye in which the natural crystalline lens has been replaced with an intraocular lens.
Before an intraocular lens is placed into a patient's eye, a doctor or other personnel typically selects an intraocular lens that is designed to provide desired refractive correction for the patient's eye. For example, an intraocular lens could have an optical lens designed to correct myopia (near-sightedness), hyperopia (far-sightedness), astigmatism, or other refractive errors that occur naturally in the patient's eye. However, it is often the case that the intraocular lens selected for a patient's eye does not fully correct (and may even cause) some form of refractive error in the patient's eye. This refractive error is referred to as “residual” refractive error.
There are various conventional options for correcting residual refractive error, all of which have their disadvantages. For example, one intraocular lens in a patient's eye could be replaced with a different intraocular lens, but this typically has a high risk of surgical complications. Ablation surgery (such as LASIK) on the cornea of a patient's eye could be done to correct residual refractive error, but this can have a high level of unwanted side effects, particularly for older patients. An additional intraocular lens (often referred to as a “piggyback” IOL) could be inserted in front of an existing intraocular lens, but this is typically an invasive procedure with less predictability associated with the final refractive outcome. In addition, intracorneal lenses (ICLs) can be inserted into the cornea of a patient's eye, but this is often more invasive and has a high degree of rejection. In general, the above procedures are typically not predictable and have a higher degree of surgical risk. Also, the devices used in the above procedures are difficult to remove and “reverse” any residual refractive error, resulting in a higher risk of leaving the patient with induced visual aberration.